Remote control system



1936- R. G. RICHARDSON ET AL 2,049,622

REMOTE CONTROL SYSTEM Filed March 30, 1923 3 Sheets-Sheet 1 l'zTfiTfisEuunsgE- Emhardsun -Jnhu 'I. Bellamy HIT y:

1936- R. cs. RICHARDSON ET AL 2,049,622

REMOTE CQNTROL SYSTEM Filed March 50, 1923 3 Sheets-Sheet 2 HIT.-

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R. G. RICHARDSON ET AL REMOTE CONTROL SYSTEM Filed March 30,- 1923 3Sheets-Sheet Imren Ursa haw s Inn-- J0 4%.

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Patented Aug. 4, 1936 UNITED STATES REMOTE CONTROL SYSTEM Rodney G.Richardson and John I. Bellamy, Chicago, Ill., assignors, by mesneassignments, to Associated Electric Laboratories, Inc., Chicago, Ill., acorporation oi. Delaware Application March 30. 1923, Serial No. 628,723

12 Claims.

The present invention relates to remote control systems in general, butmore particularly to such remote control systems as are suitable for usein connection with remotely controlled electric substations; and asregards some of its features, may be considered an improvement on theco-pending application of Nelson, filed November 16, 1921, Serial No.515,664, Patent No. 1,765,538, dated June 24, 1930.

The broad general object of this invention is the provision of suitablecircuit arrangements for use in such a remote control system whereby thechances for error are reduced to a minimum.

Specifically, one object of the invention is to produce circuitarrangements such that the despatcher who operates the distant apparatusby means of the remote control system is enabled to check the positionor setting of the distant controlling switch before the operation he isabout to bring about takes place; and such that the despatcher canrestore the distant control switch to normal without operating thedevice corresponding to the setting of said control switch, in case hediscovers by means of the above mentioned checking arrangements that thedistant control switch is set-in some position other than that in whichhe intended to set it.

Another object is to produce suitable circuit combinations whereby thedespatcher is enabled to check the position of any piece of apparatus atthe substation either as a matter of routine or in case he suspects thatthe usual lamp indication is incorrect.

The other objects, which have to do mainly with the detailed circuitarrangements, will appear from time to time, and will be apparent as thespecification is further perused.

Referring now to the drawings comprising Figs. 1, 2, and 3, theapparatus shown in Fig. 1 is located in the despatchers oiiice and isconnected to the apparatus in the substation by means of the two pairsof conductors 41 and 48, and 49 and 50, respectively. The apparatusshown in Figs. 2 and 3 is located in the substation.

Figure 1 shows the calling device CD by means of which the despatcheroperates the control switch in the distant substation. This drawingshows also the switch D which is controlled from the substation andwhich effects the lighting and extinguishing of the associated signallamps such as L and L Figure 2 shows the control switch E, located inthe substation, which is operated by the calling comprising relays 3!",302, and 303, of which two are provided for each starter, circuitbreaker, etc. in the substation. These relays control the operation ofthe switch, D, Fig. 1, through the medium of the relay group RG and thecounting switch CS.

The substation shown is assumed to be provided for the purpose oftransforming three-phase alternating current energy which is suppliedover conductors 215-2 ll, inclusive, Fig. 2, into direct current energywhich is supplied to the bus-bar 260. The motor of the motor generatorMG is operated in the well-known manner by the threephase alternatingcurrent and the associated generator supplies the'direct current.

The motor generator MG may be placed in service by operating the starterS so as to bring the unit up to running speed, and then closing thecircuit breaker CB which connects the generator to the bus-bar 260.

The signal operating switch D, Fig. 1, and the controlling switch E,Fig. 2, are mechanically identical with each other, and are of a type ofautomatic switch disclosed in Automatic Telephony, second edition, abook published by McGraw-Hill Book Company, 370 Seventh Avenue, NewYork, N. Y. A photograph of this type of switch is shown on page 53 ofthis publication and a skeleton drawing is shown on page 58. Adescription accompanies the photograph and describes how this type ofswitch, which is a switch having a step by step vertical movement and astep by step rotary movement, operates. The circuits of the switches Dand E are shown complete and will be described fully hereinafter.

The calling-device CD, Fig. 1, may be of any one of several well-knowntypes, but for the purpose of illustration, is assumed to be of the typeshown on pages 40 and 41 of Automatic Telephony above referred to. Thefunction of this calling device, as stated hereinbefore, is to controlthe switch E in the substation over the conductors 41 and 48.

The various pieces of switching apparatus in the substation, such as thestarter S and the circuit breaker CB which are shown, may be operated atthe will of the despatcher through the medium of the controlling switchE. This operation is effected through the contacts in the bank of wiper86, as will be explained hereinafter.

The starter S is arranged as usual to be returned to normal in case thealternating current supply fails, and the circuit breaker CB is adaptedto be thrown out automatically in case the load on the generator of themotor generator unit MG becomes too great.

In order that the despatcher may be kept informed at all times of therespective positions of 60 the various pieces of switching apparatus,each piece of switching apparatus controls the supply of groundpotential to two conductors, such as the conductors H8 and H8 associatedwith the starter S, and I20 and I2I associated with the circuit breakerCB. It will be noted that one of the associated conductors is groundedin case the starter, or circuit breaker as the case may be, is at normalwhile the other conductor is grounded in case it is operated. It is overthese conductors II8--I2I, inclusive, that the various socalled callsending relay sets, such as the one comprising relays Mil-308,inclusive, are controlled. 'Each time the ground connection is shiftedfrom one of the above mentioned conductors to the other, the callsending relays associated with the newly grounded conductor operate andcause, through the medium of the calling sending relay group RG and thecounting switch CS, the signal operating switch D in the despatchersofllce to be set into a position corresponding to the new position ofthe operated device in the substation. This results in one of thedespatchers lamps becoming extinguished and another becoming lighted togive to the despatcher the correct indication.

The counting switch CS, Fig. 3, comprises two semi-circular rows ofcontacts which are wiped over by the wipers I18 and I19 under thecontrol of the stepping magnet I16. The stepping magnet I16 operates thewipers I18 and I18 by rotating the common spindle to which the twowipers are rigidly secured. These wipers are operated step by step asthe magnet is alternately energized and deenergized, being advanced uponthe deenergization of stepping magnet I16 rather than upon theenergization. One mechanical embodiment of such a switch is shown onpage 51 of Automatic Telephony hereinbefore referred to.

It is to be understood that while several batteries are indicated ineach of the drawings, there is no need ofhaving more than one battery inthe substation and one battery in the despatchas office, the severalbatteries being shown for the sake of simplicity.

Although the starter S and the circuit breaker CB, Fig. 2, are the onlypieces of substation switching equipment shown, it will be understoodthat in actual practice a great many more similar devices will be foundin each substation. In

view of the fact that substations and their eouipment are well known, noattempt has been made to show the substation layout in any great detail,only so much being shown as will be needed to describe. and explain thevarious features of the present invention.

It has been assumed that there are several other units of switchingapparatus in the substation, which may or may not be similar to thestarter S and the circuit breaker CB. It is assumed further that eachswitching unit has its own call sending relays such as the relays shownin the upper part of Fig. 3, which relays, as before stated, areassociated with the starter S and the circuit breaker CB. It is assumedthat some of these other sets of relays have contacts connected inseries in the two chain circuits extending through the contacts of therelays shown and being connected in the dotted portions of thesecircuits. It is assumed also that the remaining ones of the other relaysare located to the right of the relays shown in the upper part of Fig. 3as indicated by the arrowheads placed on the ends of the conductorsterminated at the right-hand edge of'the drawing.

The apparatus, having been described in general, will now be describedin connection with a detailed description of its operation. For thispurpose, it will be assumed that the despatcher decides to put the motorgenerator MG into operation. In order to do' so, the first thing thedespatcher must do is to effect the operation of the starter S.Accordingly, the despatcher operates the key K associated with thecalling device CD, thereby closing .a circuit for the slow to pull uprelay I8. This relay is made slow to pull up by placing the coppercollar on the armature end of the core rather than on the opposite endof the core. This is denoted in the drawings by the position of thecopper collar on the upper end of relay I6, which; is assumed to be thearmature end. Relay I6, therefore, does not operate its armatureimmediately. Relay I1, which is a slow-acting relay also, energizesvimmediately, however, owing to the fact that its copper collar is on theend of the core away from the armature. Upon energizing, relay I.1 opensa point in the circuit of the lower winding of relay 24 at armature 2Iand at armature 28 closes a bridge across the conductors 41 and 48 andincluding the contacts I4 of the calling device CD.

Before the effect produced by the closing of this bridge across theconductors 41 and 48 is considered, the description of the operation ofrelays I6 and I1 will be completed. Relay I6 energizes a moment afterthe energization of relay I1 opens the circuit of relay I1 at armatureI8 closes a point in the circuit of the lower winding of relay 24 atarmature I9; and at armature I8 places a shunt around armature 20 andits working contact. A moment later, slow-acting relay I1 deenergizes;opens the previously closed point in the bridge across conductors 41 and48, leaving said bridge closed through armature I8 and its workingcontact; andat armature 2I completes a circuit for the lower winding ofrelay 24 including the normally closed contacts controlled by armature39' of relay 28 and armature I9 and its working contact of relay I6.Relay 24 energizes over this circuit and prepares a locking circuit foritself at armature 3I; disconnects wiper 23 and connects up wiper 22 atarmature 32; opens a point in the circuit of the signal relay ID atarmature/ 30'; and at arma'ure 30 shifts the wiper circuit from thelocal locking conductor to the flasher F. The net result of theenergization of relay 24 is that the circuits of the switch D areshifted so that the said switch.

D will operate correctly as a checking switch when the despatcheroperates the substation switch E as will be explained subsequently. Itis necessary to make this circuit change at this time owing to the factthat the switch D is normally connected in such a. way that when it isoperated one of the lamps of a set is extinguished and another lightedas fully explained later.

The energization of relay 24 was delayed as pointed out above in orderto permit any call which may have started in the substation, but whichhas not reached the stage at which relay 28 of the switch D hasenergized, to be vcompleted before the energization of relay 24 takesplace. The above mentioned delay while only momentary is long enough toassure that any call which is already started Will have time to proceedfar enough to operate the release relay 28 of the 75 switch D, whileother calls are prevented from starting after the closure of the bridgeacross conductors 41 and 48 as will be explained fully hereinafter.

In the substation line relay 60 of the switch E energizes in response tothe above mentioned closure of the bridge across conductors 41 and-'48in the despatchers oilice and closes a circuit f or release relay 6|.Relay 6I' thereupon energizes; and removes the ground from conductor I24at This results in ground being re-' armature 68. moved from the chaincircuit passing through armature 306 and its resting contact of relay302 and the corresponding armatures on the following relays. This hasthe effect of preventing any more calls from starting until conductorI24 is again grounded. The way in which this operates to prevent callsfrom being started will be appreciated perhaps more fully as thedescription progresses.

As a further result of the energization of relay 6|, it prepares acircuit for the lower winding of switching relay 64 at armature 67, andat armature 69 opens a point in the circuit of release magnet 8! andprepares a circuit for vertical magnet 80.

Having operated the key K, as above pointed out, the despatcher nowmanipulates the calling device CD in accordance with the first digit inthe number assigned for operating the starter S. It will be assumed thatthis number is IIand, accordingly, the calling device is turned for thedigit I and produces one interruption in the bridge across conductors 41and 48. When this occurs, the line relay 60 of the switch E deenergizesonce momentarily, thereby sending an impulse of current to verticalmagnet over the following circuit: From ground by way of armature 66 andits resting contact, armature 69 and its working contact, contact of offnormal spring 84 and said spring, slow-acting series relay 62, andvertical magnet 80 to battery. By the operation of vertical magnet 80,the switch shaft is raised one step and brings the wipers and 86opposite the first level of bank contacts. Relay 62 is energized inseries with vertical magnet 80 and is made slow-acting so as to retainits armature attracted and maintain its own circuit and that of verticalmagnet 80 intact after the ofi normal springs have shifted as they do onthe first vertical step. The last part of the impulse sent to verticalmagnet 80, therefore, traverses the normally open contacts controlled byoff normal spring 84, and armature I0 and its working contact instead ofthe contact of oil normal spring 84 and said spring. In cases when it isdesired to raise the shaft of the switch E to some other level, agreater number of impulses are sent and all of them after the first aretransmitted over the same path as the last part of the first impulse'Soon after the termination of the above mentioned impulse to verticalmagnet 86, slow-acting series relay 62 deenergizes and transfers theoperating circuit from the vertical to the rotary magnet.

When the despatcher manipulates the dial of the calling device CD inaccordance with the second digit in the desired number, one interruptionis again produced in the circuit of line relay 60, whereupon said linerelay 60 deenergizes and sends an impulse of current to the rotarymagnet 82 over the following circuit: From ground by way of armature 66and its resting contact,

armature 68 and its working contact, normally open contacts controlledby oil normal spring 84, armature I0 and its resting contact, armatureI8 and its resting contact, and rotary magnet 82 to battery. Uponreceiving this impulse, rotary magnet 82 energizes and steps the switchwipers 86'and into engagement with the bank con- 1 tacts Bland 88,respectively, which are the first set of bank contacts in the selectedlevel. Relay 631 isfenergized in multiple with rotary magnet '82 andmaintains the circuit of the lower winding of switching relay 64 openuntil the switch wipers have come to rest on the selected contacts.Relay 63 'is made slow-acting so that it will re--' tain its armatureattracted between succcessive impulses when the number of rotary stepstaken exceeds one. Shortly after the termination of the rotary movement,relay 63 deenergizes, thereby connecting up the lower Winding of relay64 at armature 12. When this occurs, relay 64 and relay 303, Fig. 3,energizes in series over the following circuit: From ground by way ofarmature I59 of relay MI in the relay group RG, Fig. 3, and its restingcontact, armature I41 and its resting contact, conductor I23, armature61 and its working contact, resting contact of armature I2 and saidarmature, lower winding of switching relay 64, normally closed contactscontrolled by armature I6, wiper 85, bank contact 81, conductor IIO,resting contact of armature 304 of relay 3M and said armature, and relay303 to battery. Relay 64 of the switch E and relay 303 energize inseries overthe above traced circuit. Due to its adjustment relay 64energizes first and closes a locking circuit for its upper winding atarmature I5, which locking circuit includes the working contact ofarmature 68 and said armature; disconnects rotary magnet 82 at armature,I8; prepares a circuit for relay 65 at armature 11; places ground onconductor I22 at armature 14, thereby preparing a circuit for relay I35of the relay group RG which will be closed subsequently; and at armatureI6 short circuits and then opens its own lower winding, thereby applyingdirect ground to wiper .85.

Relay 303, Fig. 3, upon energizing over the above traced circuit, closesa locking circuit for itself at armature 301 which includes the normallyclosed contacts controlled by armature I64 of relay I43 in the relaygroup RG. As a further result of the energization of relay 303, itconnects the first impulse stop conductor I8I to the first digit andsecond digit stop conductors I28 and I21 at armatures 309 and 3l0,respectively, thereby preparing the circuits for sending in the numberII to the despatcher; prepares a circuit for relay 30I at armature 308;and at armature 3II places ground on conductor I26, thereby closing acircuit for relays I40 and MI in multiple. Relays I40 and I4I energize,but the energization of relay I4I does not have any particular functionat this time. Relay I40, upon energizing, places ground on conductor I29, thereby completing the circuit of relay 30I by way of the workingcontact of armature 308 and .1.

said armature. Relay 30I thereupon energizes but does not have anyparticular function at this time. As a further result of the groundpotential being placed on conductor I26 in response to the energizationof relay 303, a circuit is closed by way of armature I 54 and itsresting contact for relay I42. Relay I42, upon energizing, closes abridge across conductors 49 and 50 at armature I62 includingarmaturesI65 and I6! and their resting contacts in multiple; places ground onarmature I84 at armature I88; and at armature I8I closes a circuit forrelay I48. Relay I43, upon energizing, places a multiple ground onconductor I28 at armature I83, and at armature I84 shirts the lockingcircuit of relay 383 so as to Include the working contact of armatureI84 and said armature and armature I68 and its working contact insteador the normally closed contacts controlled by armature I84. This is doneso as to permit a release of relay 383 at the proper time, as will beexplained subsequently.

In the despatcher's oflice line relay 29 of the switch D energizes inresponse to the closure of the above mentioned bridge across conductors49 and 68 in the relay group RG, and closes a circuit for release relay28 at armature 4I. Upon energizing, release relay 28 opens a point inthe circuit of release magnet 44 and prepares a circuit for verticalmagnet 41 at armature 48; connects the flasher F to wiper 22 at armature38; and at armature 39' closes a locking circuit, for

.the upper winding of relay 24 by way or armature 3I and its workingcontact and opens the circuit of the lower winding 0! the said relay 24.The switch D is now in readiness to be operated under the control of thesending equipment in the substation.

Returning now to the relay group R6, as a still further result of theground potential being placed on conductor I26 as describedhereinbefore, a circuit is completed for the sending relay I44 by way ofthe armature I54 and its resting contact, resting contact of armatureI69 and said armature, sending relay I44, and the constantly rotatinginterrupter I to battery. Sending relay I44 now starts to vibrate underthe control of the interrupter I. Upon the first effective energizationof relay I 44, a circuit is completed for stepping magnet I16 of thecounting switch CS at armature I66, whereupon said magnet I16 energizesand attracts the armature I11, thereby causing the associated pawl toengage another notch in the wiper driving ratchet wheel. Upon the nextdeenergization of relay I44, stepping magnet I16 deenergizes also onaccount of its circuit being opened at armature I66, and upon armatureI11 being retracted the wipers I18 and I19 are advanced into engagementwith the first set of their bank contacts. When wiper I18 comes intoengagement with its first associated bank contact, it closes a circuitfor pick-up relay I45. Pick-up relay I45 thereupon energizes and removesa shunt from around the armature I65 of relay .I44 and its restingcontact at armature I61 so as to render each of the subsequentenergizations of relay I 44 effective in interrupting the bridge acrossconductors 49 and 58.

Upon the next energization of relay I44, the bridge across conductors 49and 58 is opened at armature I65 and stepping magnet I16 of the countingswitch CS is energized again. Upon the subsequent deenergization ofsending relay I44, the bridge across conductors 49 and 50 is againclosed and the circuit of stepping magnet I16 is opened, whereupon thewipers I18 and I19 are advanced into engagement with the second set ofassociated bank contacts. Since the number to be called is 11 and thefirst digit of that number is 1, it is now necessary to terminate thefirst digit. That being the case, the first impulse stop conductor I8Iis connected to the first digit stop conductor I28 through armature 369and its working contact, and ground is accordingly extended to thesecond contact in the bank of wiper I19, thereby energizing stop relaycircuit of stepping magnet I 18 and the circuit I48. Upon energizing,stop relay I48 opens the circuit of sending relay I44 at armature I88;closes a-locking circuit for itself at armature I 19'; and at armatureI1I connects stepping magnet I18 to wiper I18 through interruptercontacts I15. Stepping magnet I18 accordingly operates in a buzzer-likemanner and rotates the wipers I18 and I88 step by step until they passof! the last set of bank contacts, thereby opening the oi theslow-acting relay I45. Relay I45, being slow-acting, does-not deenergizeimmediately.

Counting relay I38 is energized in multiple with slow-acting relay I48through armature I58 and its resting contact and armature I52 and itsresting contact. Upon energizing, counting relay I88 closes a lockingcircuit for itseli through counting relay I31 at armature I58. Thislocking circuit does not become effective, howe'ver, untilthe initialcircuit is broken and relay I31 is not energized at this time owing tothe fact that it is grounded at both terminals.

Upon deenergizing after an interval, slow-acting relay I45 replaces the.shunt around annature I66 and its resting contact of sending relay I44at armature I61 and at armature I68 opens the locking circuit of stoprelay I46 and also the initial circuit of counting relay I 36. When thisoccurs, the locking circuit of counting relay I36 through counting relayI31 becomes effective andrelay I31 energizes in series with relay I36;opens a still further point in the initial circuit of relay I36 andprepares a circuit for counting relay I38 at armature I52; and atarmature I 5| disconnects ground from the first digit stop con- 3 ductorI28 and places ground on the second digit stop conductor I 21.

Upon deenergizing, relay I46 opens a still further point in its lockingcircuit at armature I10; disconnects stepping magnet I16 from Wiper I184 at armature HI; and at armature I69 again con nects up sending relayI44,

Relays I44 and I46 and the counting switch CS now repeat the abovedescribed operations with the result that the second digit 1 is sent 4out in the same manner as the. first digit 1 except. that the stop relayI46 is energized in the second case from the second digit stop conductorI21 and through the working contact of armature I5I instead of from thefirst digit stop con- 5 ductor I 28 as in the first case.

Upon the circuit being closed for stop relay I46 the second time, relayI46 energizes with the hereinbefore described results, and also acircuit is closed for counting relay I38 in multiple with 5 relay I46and in series with armature I56 and its resting contact and armature I52and its working contact. Upon energizing, relay I38 closes a lockingcircuit for itself through counting relay I39, which locking circuitdoes not be- 6 come efiective until the initial circuit of relay I38 isopened. When the initial circuit of counting relay I38 and the circuitof relay I46 are opened upon the deenergization of relay I45 after thetermination of the second digit 1, the locking 6 circuit for relay I38through the counting relay I39 becomes efiective and counting relay I39,upon energizing, opens the circuit of relays I42 and I 44 at armatureI54; opens another point in the initial circuit of relay I38 at armatureI56; and at armature I55 closes a circuit for relay I35 as follows: Fromground by way of the working contact of armature 14 of the switch E andsaid armature, resting contact of armature 1I and said armature,conductor I22, armature I55 75 and its working contact, and relay I35 tobattery. Upon energizing, relay I35 closes a locking circuit for itselfat armature I48; disconnects conductor I23 from the resting contact ofarmature I59 of relay I4I at armature I41; and at armature I49 places amultiple bridge across conductors 49 and 50 so as to hold up the switchD in the despatchers ofiice for a purpose to be explained hereinafter.

As the result of the circuit of slow-acting relay I42 being opened, thisrelay deenergizes after an interval and opens the initial bridge acrossconductors 49 and 50 .at armature I62, leaving said bridge closed byrelay I 35; opens the circuit of slow-acting relay I43 at armature SI;and at armature I60 opens the locking circuit of relay 303. Relay I43,beingslow-acting, remainsenergized for an interval after its circuit isopened, and maintains the locking circuit of relay 303 open at thenormally closed contacts controlled by armature I64 long enough topermit relay 303 to deenergize. Upon deenergizing, relay 303 opens afurther point in its locking circuit and closes a point in the chaincircuit at armature 301; removes ground from conductor I26 at armature3| I, leaving said conductor grounded at armature I63 of relay I43; andat armature 30B opens the circuit of relay 30I. Relay 30I, upondeenergizing, prepares a circuit for relay 302 at armature 305, and atarmature 304 closes a point in the initial energizing circuit of relay303 through wiper-85 of the switch E. This circuit is not completed andrelay 303 does not energize again at this time owing to the fact thatground has been removed from conductor I23 at armature I59 of relay I Mas explained hereinbefore, thereby removing ground from wiper 85.

After an interval slow-acting relay I43 deenergizes, thereby replacingground on conductor I25 at the normally closed contacts controlled byarmature I64 and removing ground from conductor I26 at armature I63,whereupon relays I36-I4I, inclusive, deenergize, leaving the relays inthe relay group RG all deenergized with the exception of the holdingrelay I35 which is locked up switch E.

The operation of the switch D in the despatchers oflice in response tothe calling of the number I I by the call sending equipment in thesubstation as described above will now be taken up. When line relay 29deenergizes in response to the first interruption representing the firstdigit I in the number, it closes a circuit for vertical magnet 41 by wayof armature 40 and its working contact, contact of off normal spring 46and said spring, and series relay 21. Vertical magnet 41 operates in thesame manner as the vertical magnet 80 of the switch E as explainedbefore and raises the switch shaft one step, carrying the switch wipers22 and 23 opposite the first level of bank contacts. Slow-acting seriesrelay 21 is energized in series with vertical magnet 41 and performs thesame function as series relay 62 of the selector E hereinbeforedescribed. After the termination of the impulse sent to the verticalmagnet, series relay 21 deenergizes and transfers the operating circuitto the rotary magnet 42.

In response to the interruption in its circuit representing the seconddigit I in the number I I, relay 29 deenergizes and sends an impulse ofcurrent to rotary magnet 42 by way of armature 40 and its workingcontact, normally open contacts controlled by off normal spring 46,armature 38 and its resting contact, and armature 36 and its restingcontact. Rotary magnet 42 responds to this impulse of current bystepping the switch wipers 22 and 23 into engagement with the first setof bank contacts 8 and 9 in the first level. Slow-acting relay 26 isenergized in multiple with rotary magnet 42 and maintains the switchwiper disconnected during the rotary movement. Upon deenergizing, at thetermination of the rotary movement, slow-acting r ay 26 connects upwiper 22 at armature 31', thereby completing a circuit for the lamp IFtraceable from ground through the flasher F, spring 30 and its workingcontact, springs 39, 31, lower winding of relay 25, through the normallyclosed contacts controlled by springs 35,'spring 32 and its makecontact, wiper 22 and contact 9, through the lamp L to grounded battery.The lamp L3 accordingly starts'fiashing so as to attract the attentionof the despatcher and inform him that that is the lamp corresponding tothe set posi-' tion of the switch E in the substation. The rotary magnetcut-ofi relay 25 energizes in series with the lamp L shorts its lowerwinding at armature 35; locks itself at armature 34 over a circuitincluding the upper winding of relay 25, armature 34 and its makecontact, armature 39' and its make contact to ground; and at armature36. disconnects rotary magnet 42 and relay 26 from the operating circuitso as to prevent their unnecessary operation during the subsequentrelease of the switch D.

In order to facilitate the explanation, it will be assumed for the timebeing that due to an error by the despatcher in operating his callingdevice CD or due to a false operation of the switch E, Fig. 2, the saidswitch E landed upon a set of contacts other than the first set in thefirst level as assumed hereinbefore. That being the case the callsending mechanism at the substation fails to operate the switch D orelse causes the switch D to be set on a set of contacts other than theones with which the lamp I. is associated. Whether the call sendingmechanism responds or not depends upon whether the conductor associatedwith the contact on which the wiper 05 of the' switch E actually landsis connected through to the associated call sending relay such as 303for'example (see conductor H0) or is disconnected by the associatedcut-ofl. relay such as 30I for example (see conductor III). In this caseno lamp is flashed or else the wrong lamp is flashed, and in either casethe despatcher is informed that the substation switch is not on thedesired set of contacts.

Assuming at any rate that the desired lamp does not start flashing, thedespatcher releases the switch E at this stage without operating thedevice for which it is set. In order to do this, he merely releases thekey K which he has been holding operated during this time, therebyopening the circuit of relay I6 and permitting it to deenergize. Upondeenergizing, relay I6 opens the bridge across conductors 41 and 48,whereupon line relay 60 of the switch E deenergizes and sends an impulseof current over the previously traced operating circuit to the relay 63.Relay 63, upon energizing at this time, opens the locking circuit ofholding relay I35 in the relay group RG at armature 1 I, whereupon relayI35 deenergizes and opens the bridge across conductors 49 and 50,permitting the switch D to release In qjaanner to be describedsubsequently. A momentjifter the deenergization of line relay 60,slow-acting release relay 6| deenergizes due to the prolonged opening ofits circuit, thereby bringing about the release of the switch E in amanner to be described subsequently.

Returning now to the original assumption that the switch .E operated asthe despatcher desired and that the switch D was set on the contacts 8and 9 with the result that the lamp I. started flashing, the despatcher,upon noting that the desired lamp is flashing, knows that the switch E.is set in the desired position and not in some other position. Thedespatcher now operates his calling device CD in accordance with anydesired digit, the digit -1, for example, thereby producing a momentaryinterruption in the circuit of line relay 60 of the switch E, whereuponthe line relay 60 deenergizes momentarily and sends an impulse ofcurrent to slow-acting relay 63, resulting in the energization of saidrelay 63. Relay 63, being slow-acting, maintains its armature attractedfor an interval after the termination of this impulse and at armature Hopens the locking circuit of holding relay I35, Fig. 3, whereupon relayI35 deenergizes and opens the bridge across conductors 49 and 50. As afurther result of the energiza tion of relay 63 of the switch E, itprepares a circuit for relay 65 at armature I3. When line relay 60energizes again after its momentary deenergization, it completes acircuit for relay 65 as follows: From ground by way of armature 66 andits working contact, working contact of armature I3 and said armature,working contact of armature I1 and said armature, and relay 65 tobattery. Upon energizing, relay 65 places ground on wiper 86 at armature19 in order to operate the starter-S.

After having manipulated his calling device for the digit 1 to initiatethe operation of the starter S as described above, the despatcherreleases the key K, thereby opening the circuit of relay It. It may bepointed out that the off normal spring I 5 comes into engagement withits associated contact .as soon as the dial of the calling device isturned ofi normal, thereby closing a circuit tor relay I6 independent ofthe key K so as to maintain the relay I6 energized a sufllcient lengthof time in case the despatcher happens to release the key K too quicklywhile the calling device is returning to normal after having beenoperated the last time. Upon deenergizing, relay l6 opens the bridgeacross conductors 41 and 48 at armature l8, whereupon the line andrelease relays oi the switch E. deenergize one after the other, andrelease relay 6|, upon deenergizing, opens the operating circuit andcloses the release magnet circuit at armature 69, and at armature 68removes ground irom the locking armature 15 of relay 64 and replacesground on the chain conductor I24. Relay 65 deenergizes in response tothe'falling back of armature 66 of line relay 60 and removes ground fromwiper 86 and relay 64 deenergizes in response to the opening of itslocking circuit by release relay 6|. Release magnet 8| energizes inresponse'to the deenergization of release relay 6! and is energized overthe following circuit: From ground by way of armature 66 and its restingcontact, armature 69 and its resting contact, off normal contacts 83,and release magnet 8| to battery. Upon the energization of releasemagnet 8|, the shaft and wipers of the switch E are restored to normalposition, and the circuit of release magnet 8| is opened at ofi normalcontacts 83 by the switch shaft when the latter reaches its normalposition.

The line and release relays 29 and 28 of the switch D in the despatchersomce deenergize one after the other in response to the opening of thebridge across conductors 48 and 58 in the substation as pointed outhereinbefore. In response to the deenergization of release relay 28,armature 39' is retracted and the circuit-oi relays 24 and 25 is opened,whereupon these relays deenergize. As a further result of thedeenergization of release relay 28, thecircuit of release magnet 44 isclosed the same is in engagement with bank contact 88 as explainedhereinbefore.

Upon energizing, relay 2 closes a locking circuit for itself at armature246 in series with the resting contact of armature 232 and saidarmature; closes a circuit for the solenoid 230 through armature 244 andits, resting contact at armature 245; and at armature 241 'closes acircuit for relay 240 through the resting contact of armature 242 andsaid armature. Relay 240 does not energize immediately, however, owingto the fact that it is wound so as to be highly inductive and owing alsoto its stifi adjustment. In response to the closing of the circuit ofthe solenoid 230, said solenoid 238 energizes and attracts the plunger228, thereby rotating the operating lever in such a direction as toswing all of the pivoted switches 2|8-223, inclusive, to the left. Thisresults in the three-phase auto-transformer being connected to thethree-phase supply leads 2| 5-2", inclusive. The switch levers 221-223,inclusive, connect the three conductors of the three-phase inductionmotor of the motor generator MG to the reduced potential taps of theauto-transformer. When this occurs, the motor generator MG starts topick up speed and, as usual, draws a very heavy current for starting.This heavy'current is sufficient to operate the relay'238 which isshunted around resistance 224 connected in one of the auto-transformerleads. Relay 238 energizes before the slow to energize relay 240 has hadtime to energize and opens the circuit of the latter.

When the motor generator MG has picked up suflicient speed to approachsynchronism, the intake of current is no longer sumcient to main- I tainthe marginally adjusted relay 238 energized.

Accordingly, relay 238' deenergizes and closes the circuit of relay 240at armature 242. I Relay 240, upon energizing after the interval forwhich it is adjusted, attracts armature 244, thereby opening the circuitof solenoid 230 and closing a circuit through solenoid 23L When thisoccurs, the plunger 229 is attracted and the operating lever 226 swingsthe switch arms 2|8-223, inclusive, to the right, thereby disconnectingthe auto-transformer from the line and connecting the three conductorsof the motor direct on to the line instead of to the low potential taps.One of the conductors through which current is now supplied to the motoris cut and the' resistance 228 is inserted therein. The holding magnet233 is connected in shunt of resistance 228 through armature 243 and itsresting contact. Holding magnet 233 accordingly energizes and attractsits armature 232 which engages the end of the lever 226, thereby holdingsaid lever in its operated position independent of the solenoid 23L Theattraction of armature 232 results in the locking circuit of relay 24]being broken. Relay 24I, upon deenergizing, opens the circuit of relay240 at armature 241, whereupon relay 240 deenergizes and opens thecircuit of solenoid 23I, leaving the lever 226 under the control ofarmature 232 which holds said lever 226 in its operated position. Themotor generator MG is now up to speed and is ready to carry its portionof the load.

As a further result of the starter S being thrown to running position,ground is removed from conductor I I9 and placed on conductor 8. Whenthis occurs, the cut-off relay which is shown locked up over conductorII9 deenergizes and relay 302 is energized over conductor H8 througharmature 305 and its resting contact. Upon energizing, relay 302 opensthe chain circuit so as to render the energization of any one of theother similar relays ineifective in case it should occur at this time.Relay 302 also closes a circuit for relay 303 at armature 306 asfollows: From ground by way of armature 68 and its resting contact,chain conductor I24, armature I58 and its resting contact, armature 306and its working contact, and relay 303 to battery. Upon energizing,relay 303 opens at armature 301 the chain circuit extending to the othersimilar relays so as to unlock any of them that might have just becomelocked up over this chain circuit. These two chain circuits, it may bepointed out, are used in order to secure the desired effect that onlyone relay, such as 303, can remain energized while a call is being sentin to the despatchers office. Otherwise, two or more such relays mightbe energized at the same time and prevent the successful operation ofthe call sending equipment. As a further result of the energization ofrelay 303, it closes a locking circuit for itself at armature 301 whichincludes the locking conductor I25 which is grounded .by way of thenormally closed contacts controlled by armature I64 of relay I43;prepares a circuit for relay 30I at armature 308; connects up the firstand second digit stop conductors to the first impulse stop conductor I8Iat armatures 309 and 3I0; and at armature 3II places ground on conductorI26 with the hereinbefore described results that relays I40 and MI areenergized. Relay I40, it may be explained at this time, is highlyinductive and stifily adjusted and for these reasons does not energizeimmediately. Relay I4I, however, energizes right away and opens atarmature I58 another point in the chain circuit extending througharmature 306 and its resting contact and similar armatures and contactson the corresponding relays in the other sets. This is done to preventthe operation of any relay set irom being interfered with by a precedingrelay set after the operation has progressed thus far. While thisoperation has no particular utility at this stage of the operation inthis particular case, it is a. very necessary operation when the callsending relay set in operation is one of the sets other than the firstin the chain. After an interval, the slow to pull up relay I40 energizesand places ground on the common conductor I29, thereby closing a circuitfor cut-off relay 30I through the working contact of armature 308 andsaid armature. Relay 30I, upon energizing, disconnects conductor IIOfrom relay 303 at armature 304, and at armature 305 opens the circuit ofrelay 302 and locks itself to grounded conductor I I8 to spring 305 andits make contact. Relay 302, having completed its operation, nowdeenergizes.

' It can probably now be understood just why the grounding of the commonconductor I29 was As a further result of the placing of ground onconductor I26 by relay 303, relay I42 operates to close a bridge acrossconductors 49 and 50 at armature I62, and the remaining relays I43-I46,inclusive, together with the counting switch CS operate as describedhereinbefore to send in the number II to the control switch D in thedespatchers oflice. At this time since the switch E is not operated, theconductor I22 is not grounded and holding relay I35 does not energizeafter the call has been sent in and the switch D is, therefore,rel-eased upon the opening of the bridge across conductors 49 and 50 atarmature I62 when relay I42 deenergizes, which it does as described inthe preceding example.

It will be remembered that, as explained hereinbefore, the slow-actingrelay I43 maintains conductor I26 grounded at armature I63 after theground has been removed from the said conductor I26 at one of the callsending relays, such as relay 303. This is done so as to prevent anothercall from being sent in to the despatchers office before the switch Dhas had time to return to normal. The line circuit of the switch D isopened at armature I62 by relay I42, which relay opens the circuit ofslow-acting relay I43 at the same time. Another call cannot be sent in,however, until after the slow-acting relay I4I, which is maintainedenergized over conductor I26, has deenergized and closed the chaincircuit at armature I58. This interval is that required for the twoslow-acting relays I43 and MI to'fall back one after the other, and issufliciently long to permit the switch D to be completely restored tonormal position.

In the despatchers office, since the despatcher is not making a call,relay 24 is not energized and,

wipers 22 and 23, a circuit is closed for the pilotrelay I0 as follows:From ground by way of the working contact of armature 3i and saidarmature, armature 30' and its resting contact, and

pilot relay I0 to battery. Pilot relay I0, upon energizing, closes alocking circuit for itself at armature I3, and at armatures II and I2,closes the circuits for the lamp L and the buzzer B so as to inform thedespatcher both visually and audibly that a call is coming in. Also,since-relay 24 is not energized. the wiper 23 instead of the wiper 22 isconnected up to the lower winding of relay 25, and as soon as theslow-acting relay 26 deenergizes after the switch wipers have been seton the contacts 8 and 9, relays 25 and 2 energize in series over thefollowing circuit: From ground by way of the resting contact of armature30 and said armature, armature 39 and its working con tact, armature 31'and its resting contact, lower winding of switchir: relay 25, normallyclosed contacts controlled by armature 35, armature 32 and its restingcontact, wiper 23, bank contact 9, relay 2, and the associatedresistance to battery. Due to its lighter adjustment, relay 25 energizesfirst over this circuit and closes the previously traced locking circuitfor itself at armature 34;

contact, and the .lamp L to battery. Accord-.

ingly, the lamp L starts flashing under the control of the flasher F.The lamp is made to flash at this time so as to give the despatcherimmediate indication of the particular set of lamps in which the changehas occurred. This obviates any necessity for a checking operation bythe despatcher.

The despatcher, after having been informed by the buzzer B and the pilotlamp L that a call is coming in, operates the push button P, therebyopening the locking circuit of the pilot relay I0, whereupon said relayI0 deenergizes and extinguishes the lamp L and disconnects the buzzer B.

After having taken sufllcient note of the set of lamps in which thechange has occurred, the despatcher operates the locking key K to itsalternate position by pushing the locking push button shown, therebydisconnecting the working contact of armature 5 from ground by way ofthe flasher F and connecting it to ground direct. This causes the lamp Lto stop flashing and to light steadily. This operation also serves toprepare a flashing circuit for the lamp L which becomes effective uponthe subsequent deenergization of the relay 2.

The switch D is released at this time in the hereinbefore describedmanner.

In order to put the motor generator MG finally into operation, it isnecessary that the circuit breaker CB be thrown in. In order to effectthis operation, it is necessary for the despatcher to close the bridgeacross line conductors 41 and 48 and then dial the number assigned tothe throwing in of the circuit breaker CB. This number, it will beassumed, is I9. Accordingly, the despatcher operates the key K with thehereinbefore described results and then operates his calling device CDfor the two digits 1 and 9 in the number 19.

In response to the operation of the calling device CD in accordance withthe digit 1, the wipers or" the switch E are raised opposite the firstlevel of bank contacts, and in response to the operation of the callingdevice CD in accordance with the second digit 9 of the number, thewipers and 86 are brought into engagement with the ninth set of bankcontacts in the first level, which are the contacts 9| and 92.- Whenwiper 85 is grounded at the cessation of the.rotary movement, ground isplaced on bank contact SI and is extended through conductor II2 to thethird set of relays, counting from the left, shown in the upper part ofFig. 3. This results in these relays operating in the same manner asdescribed for relays 30I-303, inclusive, and the number 19 is sent in tothe substation by the calling sending equipment, thereby bringing thewipers of the switch D in the substation into engagement with the ninthset of bank contacts in the first level. This results in the associatedlamp being flashed in the usual manner, thereby giving the despatcherthe indication that the switch E is on the right set of bank contacts.It will be noted I that the number 19 is sent out by the call sendingequipment in this case'instead of the number 11 described in thepreceding case, owing to the fact that the ninth impulse stop conductorI89 is used to terminate the second digit ratherthan the first impulsestop conductor I8I.

The despatcher now operates the calling device CD again i or der tothrow in the circuit breaker CB and, hen this occurs, the wiper 86 isgrounded momentarily as hereinbefore described, with the result that theground potential is extended by way of bank contact 92 and conductor II6 to the solenoid 25B of the circuit breaker CB. The momentaryenergization of solenoid 256 results in the plunger 255 being attracted,whereupon the lever 254 is rotated, thereby connecting the switch arm253 with the lead extending to the bus-bar 260-. The armature 2 51 oftrip magnet 258 is provided with the notch in the upper end in which theend of the lever 254 catches,

thereby holding the circuit breaker in its operated position. The lever254 also ungrounds conductor I2I, thereby causing the associated lockedup relay to deenergize, and places ground on conductor I20 with theresult that the call sending equipment is again operated to send in thenumber I9 to theswitch D in the despatchers office, which has beenreleased in the hereinbefore described manner in the meantime owing tothe deenergizatlon of holding relay I35 which occurred in response tothe last mentioned operation of the calling device CD.

The switch E is released in the usual manner when the despatcherreleases the key K afterhaving brought about the operation of thecircuit breaker CB.

It will be noted that in case the alternating current supply to themotor of the motor generator MG is interrupted, the holding magnet 233is deenergized, whereupon the armature 232 is retracted and the starterreturns to its normal position. When this occurs, the ground potentialis removed from conductor II8, allowing the locked up relay 30I todeenergize and a ground potential is placed on conductor HQ with theresult that the number I2 is sent in by the call sending equipment,which results in the wipers 22 and 23 of the switch D being brought intoengagement with the bank contacts 6 and 'I which are the second set ofbank contacts in the first level. When this occurs, the wiper 23 placesground on bank contact I, thereby short circuiting the relay 2 andcausing the said relay 2 to deenergize. The switch D is then releasedautomatically in the usual manner. The deenergization of relay 2 resultsin the lamp L becoming extinguished and. the lamp L being connected upto the flasher F through the working contact of the lower spring of theassociated key K and said spring, resting contact of armature 5 and saidarmature, and armature 4 and its resting contact. The despatcher, uponnoting the flashing condition of the lamp L knows that the starter S hasreturned to normal. The despatcher causes the lamp L to light steadilyby retracting the plunger of the key K and allowing the springs thereofto assume their normal position. 1

The despatcher may in this case take such steps as he may deemnecessary, either reoperating the starter S immediately or waiting asufficient length of time to permit the supply of current to the leads2I5-2II, inclusive, in. the substation to be replaced.

Although it is not shown as such, the circuit breaker CB is preferablyof the typehaving a suitable circuit arrangement for tripping thecircuit breaker in case the current is reversed. Assuming the circuitbreaker CB to be a reverse current circuit breaker, it is trippedimmediately after the starter S is returned to normal, owing to the-factthat the motor generator MG slows down and the generator there- 01starts to run as a motor, taking current from the bus-bar 260. Thecircuit breaker CB has the resistance 259 energizes and trips thecircuit breaker. This results in ground being removed from-conductor I20and placed on conductor Ill. The result of ground being placed onconductor I2I is that the associated relay group is operated and thecall sending equipment sends in the number I due to the fact that thefirst and tenth impulse stop conductors I8I and I90, respectively, areassociated with this relay group. This causes the switch D in thedespatcher's office to operate in the usual manner to give thedespatcher the necessary signal.

It has been shown above how either the starter S or the circuit breakerCB can be returned to normal owing to an abnormal condition in thesubstation. It will now be explained how. the despatcher himself caninitiate either of these operations. In order to restore the circuitbreaker CB, the despatcher dials the number 10, causing the wipers 85and 86 ofthe switch E to be brought into engagement with the tenth setof bank contacts in the first level. Then, when the despatcher gives thecalling device CD the extra operation after receiving the usualindication that the switch E is on the right contacts, the bank contact94 is grounded by the wiper 86 and trip magnet 256 of the circuitbreaker CB is operated over conductor III.

Similarly, the starter S can be restored by the despatcher who for thispurpose closes the line circuit of the switch E by means of the key Kand then dials the number I2, thereby causing the wipers 85 and 86 ofthe switch E to be set upon the bank contacts 89 and 90. The despatcherthen gives the calling device CD a further turn, after having receivedthe usual indication that the switch E is on the desired set ofcontacts, thereby causing a ground potential to be supplied to bankcontact 90 by way of the wiper 86. This ground potential extends by wayof conductor II to relay 239 in the starter S which thereupon energizesand opens the circuit of holding magnet 233, whereupon the starter S isreturned to its normal position, with the result that the correspondingnumber I2 is sent in to the despatchersoflice by the call sendingequipment in the manner described above.

In case the despatcher has any reason to believe that the lampindication of the position of any particular substation switchingdevices is incorrect, he may verify his opinion or, at any rate,ascertain the true position of any particular switching device such asthe starter S, for example, by' closing the line circuit of the switch Eand dialling either one of the two numbers assigned to that device. Incase the lamp L,

Fig. 1-, is lighted, indicating that the starter 8 is at normal, thedespatcher may verify this by dialling the number II, with theresultthat the lamp'll starts flashing as hereinbeiore described in case thestarter is actually at normal, while '6 ii the lamp L indicates that thestarter is at normal at a time when the starter is actually in I itsoperated position, the despatcher'will not be able to receive anyresponse when he dials the number 11 for thereason that cut-oil! relayIIII will be operated at that time and the lead III! will bedisconnected from relay 803 at armature 304.

In this case the despatcher will probably want still furtherverification in order that he may 15 be absolutely sure of the positionof the starter S and he will, therefore, dial the number 12,

whereupon the switch E through its wiper 86 places ground on conductorIII which is not at this time disconnected from the associated relay inFig. 3, and, as a result, the call sending equipment sends in the number12 resulting in the flashing of the lamp L.

It will be seen from the foregoing that the present system is aconsiderable improvement over prior systems of the same nature in thatthe despatcher is enabled to ascertain the position of the substationswitch before he operates the device associated with that position ofthe switch. It will be seen further that the des- 80 patcher is enabledto check the indicated position of any piece of switching apparatusagainst the actual position.

What we claim is:

1. In a remote control system, a calling device, 85 a control switch, acontrol circuit extending between said device and switch, a keyassociated with said calling device, two relays operated in response tothe operation of said key, said relays jointly, completing said controlcircuit, means for operating said control switch over saidcontrolcircuit in response to a manipulation of said calling device, andcontacts operated by said calling device for maintaining said controlcircuit completed independent of said key, while said calling device isbeing operated and for a definite interval thereafter.

2. In a remote control system, a switching device having a plurality ofpositions, a visual signal for each position of said device, meanswhereby one of said signals is operated to indi-- cate the position ofthe switching device, a circuit between said device and signal, meansfor moving said switching device to a new position, means responsivethereto and controlled over said circuit for restoring said operatedsignal to its normal condition and for intermittently operating thesignal associated with the new position of the switching device, andmanually controlled means for causing the last named signal to beoperated steadily.

3. In a remote control system, a plurality of switching devices eachhaving a plurality of positions, a set of signals for each device, onesignal of the set corresponding to each position of the associateddevice, automatic means for maintaining the proper signal operated toindicate the position of the device, means responsive to a change inposition of the device for intermittently operating the signalindicating the new position and retiring the signal indicating the oldposition of the device.

4. In a remote control system, a plurality oi. switching devices eachhaving a plurality of positions, a set of signals for each device, one

for extending a circuit to a. device to change its position, andautomatic means responsive to the extension of saidcircuit forintermittently operating the signal which indicates the position intowhich the device is to be moved.

5. In aremote control system, a plurality oi. switching devices eachhaving a plurality of positions, a set of signals for each deviceconsisting of a signal for each position of the device, automatic meansfor maintaining the proper signal operated to indicate the position ofthe device means responsive to a change in position of a device forintermittently operating the signal indicating the new position andretiring the signal indicating the old position, means for selecting adevice and moving it from one position to another, means operating inresponse to said selection to control said automatic means tointermittently operate the signal indicating the new position and tomaintain the signal indicating the old position.

6. In a remote control system, a plurality of devices each having aplurality of positions, a set of signals for each device comprising asignal for each position of the device, means for selecting a device tochange its position, an automatic switch operated in response to saidselection to intermittently operate the signal indicating the positioninto which the device is to be moved without affecting the operation ofthe signal which indicates the position in which the device stands,means for then changing the position of the device, means responsive tosaid change in position to control said automatic switch tointermittently operate the signal indicating the position into which thedevice moves and to retire the signal indicating its old position.

'7. In a remote control system, a plurality of switching devices,signalling devices, means for.

selecting a device at the substation to change its position, switchingmechanism automatically respons'ive to a change in position'oi one ofthe devices to control the signalling means to indicate that change inposition, automatic means controlled by the initiation of the operationof said first means to change the function of said switching mechanismto prevent its indication of further changes of the devices on saidsignalling means and to prepare it to indicate the position of saidselecting means, and means for delaying the change in function of saidswitching mechanism for a certain time after the initiation or theoperation of said first means to permit indications of changes alreadyin progress to be completed.

8. In a remote control system, a control circuit and a checking circuit,a step by step control switch, a calling device, a key associated withsaid calling device, means responsive to the operation of said key forcompleting said control circuit, means for operating said control switch9. In a control system, a control circuit terminating in a selectivecontrol switch, a checking circuit terminating in a selective checkingswitch, a plurality of switching devices, each having a plurality ofpositions, an indicating device for each or said switching devices, eachindicating device having a plurality of positions correspending to thepositions of the corresponding switching device, means for moving each01' said switching devices from one position to another, means includingchecking means controlled by the change of position of a device oversaid checking circuit and through the medium of said checking switch forcausing the associated indi- 10. In a remote control system, a pluralityof switching devices, a set of signals for each device, a selectiveswitch, means operating automatically inv response to a change ofcondition of any device to operate said switch to select the associatedset of signals, means in said switch for operating said signals toindicate the change in the condition of the device, another automaticswitch, means for operating said second switch to select one of saiddevices, means operated by said second switch to render said first meansunresponsive to changes in therconditions 01' said devices, and meanscontrolled by the operation of 'said second switch for operating saidfirst means to operate said first switch in a distinctive manner toindicate the position 01' said second switch.

11. In a remote control system, a plurality of switching devices eachoperable from one position to another, signalling means individual toeach of said devices, common selecting means for selecting any one ofsaid devices for operation, means for operating said device, meansresponsive to the selection of said last device for operating saidsignalling means in one manner to indicate such seizure, said means alsoresponsive to the operation of said device for operating said signallingmeans in a diiIerent manner to indicate the actual operation of saiddevice.

12. In a remote control system, a plurality of switching devices, anoperating circuit individual to each-oi said devices, signalling meansindividual to each of said devices, means for preparing the operatingcircuit of one of said devices, means responsive to the preparation 01'said circuit for operating the signalling means individual to saiddevice in one manner to indicate the said prepared operating circuit,means for completing said operating circuit to operate said device, andsaid second means reoperated responsive to the actual operation of saiddevice over said circuit for reoperating said signalling means in adiflerent manner to indicate the actual operation of said device.

RODNEY G. RICHARDSON. JOHN I. BELLAMY.

